I've successfully done this on a large range of WPL etc 1/16 trucks. I have front and rear lights plus yellow flashers and internal lights, all on one channel on the same trannie as you.
Buy the appropriate colour/functioning LEDs, all 6v, then buy a single multi-switch off eBay. This plugs into your chosen receiver channel socket, has a short cable to a very mall circuit board which has 2 or 3 two pin male pin sets, each of the pair's supplying switched 6v for your LED sets. You can add resisters to reduce brightness but because the supply is from your receiver its all 5-6v bec.
Use switch A to control the channel and you can then cycle through light sets, both single and pairs etc. The switches vary in the number of light sets supported, the combinations and price but few are more than a fiver so cheap, easy to install and use work a treat. The hardest bit is using the right words to search on ebay!

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